Translation: A planet is the cradle of mind, but one cannot live in a cradle forever.

usually cited as Earth is the cradle of humanity, but one cannot live in a cradle forever. [2]

His epitaph, written by himself (translation): Man will not always stay on Earth; the pursuit of light and space will lead him to penetrate the bounds of the atmosphere, timidly at first, but in the end to conquer the whole of solar space.

Translation: I recognize nothing that is not material. In physics, chemistry and biology I see only mechanics. The Universe is nothing but an infinite and complex mechanism. Its complexity is so great that it borders on randomness, giving the illusion of free will.

from Гений среди людей ("The Genius of the People") -- a manuscript written in 1918

** Translation: “The world is desperately imperfect. Even if a quarter of the working people were engrossed in new thoughts and inventions and lived off the others, humanity would still gain tremendously thanks to the constant stream of inventions and intellectual work emerging from this horde of people striving upward.”